This invention relates generally to the field of amplifier circuits and more particularly to a method and system for improving amplifier efficiency.
Amplifiers are used to increase or decrease voltage levels in many applications. Proper amplifier design, whether within discrete or integrated circuits, often involves tradeoffs of amplifier characteristics such as efficiency and distortion. Thus, in many applications where low distortion is desirable, performance may suffer from low amplifier efficiency.
Conventional amplifiers, including audio amplifiers, may employ a plurality of stages in order to improve amplifier performance. For example, some amplifier designs may utilize both an input stage that features characteristics such as low distortion and an output stage that resembles a class D stage that typically features higher efficiency. Such a combination may improve the total efficiency of the amplifier. However, such conventional designs may not sufficiently improve amplifier efficiency to meet a desired level of performance. For example, these conventional designs may still suffer from low signal-to-noise ratios and/or dynamic range. Therefore, it is desirable to provide a mechanism for improving amplifier efficiency while maintaining low distortion.
From the foregoing, it may be appreciated that a need has arisen for providing a system and method to improve efficiency for amplifier applications. In accordance with the present invention, a system and method are provided that substantially eliminate or reduce disadvantages and problems of conventional amplifier systems.
According to an embodiment of the present invention, there is provided an amplifier with an input stage amplifier coupled to an output node. The amplifier includes a class D output stage having at least two switching elements and coupled to the output node. The amplifier also includes a control circuit coupled to the output stage. The control circuit is operable to produce a tri-state output of the output stage in response to a sensed value proportional to an amount of current that flows to the output node. More specifically, the amplifier may comprise an audio amplifier. In another embodiment of the invention, the input stage amplifier may comprise a class AB amplifier.
The invention provides various technical advantages over conventional amplifier systems. Various embodiments of the invention may have none, some, or all of these advantages. For example, one technical advantage is to reduce switching losses of amplifiers, both in systems comprising discrete components and in integrated circuits. This advantage may increase the signal-to-noise ratio and the dynamic range of the amplifier. Another technical advantage may also be reducing electromagnetic interference of the amplifier. Yet another technical advantage may be improved power consumption over amplifiers utilizing conventional approaches. Other technical advantages may be readily ascertainable by those skilled in the art from the following figures, description, and claims.